Chapter 10: Photosynthesis 

Energy is bound into food: photosynthesis 

• All living organisms need energy, perform the processes of life – this maintains homeostasis. (7 processes of life – MRS GREN (Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition))
• Sun is the source of this energy
• Heterotrophic organisms are dependent on green plants for energy (e.g People)
• Green plants contain chlorophyll in chloroplast, can photosynthesis
• Green plants produce organic food from inorganic components, radiant energy and are therefore autotrophic
• Energy is measured in Joules, for bigger quantities, Kilojoules
• Energy occurs in many forms, two main types: Potential energy and kinetic energy
• Molecule or organism has potential energy (potential to form work)
• When work is being done, energy is converted into kinetic energy

Light: 

• Visible light is part of the whole radiation spectrum, the electromagnet spectrum
• Light moves in waves
• A wavelength is the distance between corresponding points on two consecutive waves
• One end of the spectrum (Gamma rays), these wavelengths are measured in nm
• At the other end of the spectrum (radio waves), wavelengths are measured in km
• Visible part of the spectrum is known as white light
• White light consists of a mixture of seven colours – Red, orange, yellow, green, blue, indigo, violet –
• Green plants contain chloroplasts, vast quantities of chlorophyll
• Chlorophyll – pigment that absorbs all the colours of the spectrum (except for green)
• Large quantities of energy are absorbed by the chlorophyll
• Different types of chlorophyll: Chlorophyll A is the most common type. It absorbs most of the light (radiant energy), this is converted during photosynthesis. Bright green
• Chlorophyll B: Yellowish green
• Carotenoids (Yellow and orange pigments)
• Carotenoids in plants also absorb light for photosynthesis
• The pigments absorb all light except yellow and orange

Review of the process of photosynthesis: 

• During photosynthesis radiant energy is absorbed by chlorophyll, converted into chemical potential energy bound, in carbohydrate molecule
• Glucose à C₆H₁₂O₆
• Photosynthesis takes place in two main phrases: Light dependent phase (Granum) Light independent phase (Stroma)
• Phases follow one another, occur simultaneously, there is a clear difference between the two
• Light dependent phase, takes place as long as light is available. Phase during which sunlight is absorbed by chlorophyll
• Radiant energy is converted into chemical potential energy
• Light independent phase can take place at any time during the day as long as products of the light phrase are still available

What happens after photosynthesis? 

• Glucose is the end product of photosynthesis
• Plants can convert glucose into other compounds, by various metabolic processes
• Glucose in plants is converted to starch
• Plants store excess glucose as starch
• Starch is insoluble in water
• Starch will not influence the water balance
• Proteins can be formed when plants absorb Nitrogen
• Amino acids, building blocks of proteins, formed from the nitrogen/ glucose
• Metabolic processes are catalyzed by enzymes
• Excess glucose in plants, converted onto fats and oils

Why is photosynthesis important?

Photosynthesis is a very important process

• Responsible for the maintenance of the oxygen-carbon dioxide balance
• Radiant energy can be made available to heterotrophic organisms
• The energy we use in cars and industries is also the result of photosynthesis